<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <!-- 除自身以外数组的乘积 -->
    <script>
      var productExceptSelf = function (nums) {
        let len = nums.length
        let ans = Array.from({ length: len })
        let R = 1
        ans[0] = 1
        // ans[i]等于数组i左侧所有数字的乘积
        for (let i = 1; i < len; i++) {
          ans[i] = ans[i - 1] * nums[i - 1]
        }
        // 乘上R即所有右侧元素的乘积
        for (let i = len - 1; i >= 0; i--) {
          ans[i] = ans[i] * R
          R *= nums[i]
        }
        return ans
      }
      console.log(productExceptSelf([1, 2, 3, 4]))
    </script>
  </body>
</html>
